class Solution
{
    int m, n;
    int dx[4] = { 0, 0, 1, -1 }, dy[4] = { 1, -1, 0, 0 };
    bool vis[51][51];
public:
    int maxAreaOfIsland(vector<vector<int>>& grid)
    {
        m = grid.size(), n = grid[0].size();
        int ret = 0;
        for (int i = 0; i < m; i++)
        {
            for (int j = 0; j < n; j++)
            {
                if (!vis[i][j] && grid[i][j] == 1)
                {
                    ret = max(ret, bfs(grid, i, j));
                }
            }
        }
        return ret;
    }

    int bfs(vector<vector<int>>& grid, int i, int j)
    {
        int count = 0;
        count++;
        queue<pair<int, int>> q;
        q.push({ i, j });
        vis[i][j] = true;

        while (q.size())
        {
            auto [a, b] = q.front();
            q.pop();
            for (int k = 0; k < 4; k++)
            {
                int x = a + dx[k], y = b + dy[k];
                if (x >= 0 && y >= 0 && x < m && y < n && grid[x][y] == 1 && !vis[x][y])
                {
                    q.push({ x, y });
                    vis[x][y] = true;
                    count++;
                }
            }
        }
        return count;
    }
};